Thread: Firmware 4.8.10956
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Old 05-03-2018, 02:59 AM   #193
davidfor
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Posts: 24,905
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Join Date: Jul 2011
Location: Sydney, Australia
Device: Kobo:Touch,Glo, AuraH2O, GloHD,AuraONE, ClaraHD, Libra H2O; tolinoepos
Quote:
Originally Posted by rcentros View Post
So it was all a font issue? I'm guessing the "Force user font-family" patch is what is currently allowing my ePubs to work in this firmware release on my Kobo Touch?
It is only indirectly a font issue. The issue is memory. The devices are running out of memory when opening the books. The change to in the default font has triggered the problem because of the way the the Adobe RMSDK handles them. And because of their size. And that is why the problem is being been seen more on the Touch and Glo. These only have 256MB RAM vs the 512MB in the later devices.

For the record, this is the reason that Kobo pulled the update. But, it appears it was reported to them as a problem with books sideloaded from ADE. The issue is the limited memory on these device and how it is managed:
  • The Adobe RMSDK is inefficient with how it handles the fonts.
  • The number of books the device knows about does affect this as the metadata is loaded into memory rather than continuously reading the database. That limits the memory available for other purposes.
  • Any embedded fonts take up more memory (needs these plus the fallback font for missing glyphs).
  • Adobe DRM protected books were probably worse.
  • Executables take up memory.

Of course, there are ways to handle this. An obvious one is to drop the memory used by the metadata when a book is opened. But, that would lead to the obvious complaint: "It takes ages to get back to the book list when I open a book". It is all a trade-off.

In any case, Kobo are working on this, but I don't have a idea of a release date. It is probably not to far out, but I wouldn't bet on it happening before the weekend. In the meantime, those who already have 4.8.10956 and don't see any problems shouldn't worry about it. For others, setting the default font to something other that Publisher Default or the two Kobo fonts will reduce the incidence of this occurring.

One thing I can I can't remember seeing mentioned is black covers. Another effect of this problem is that some sideloaded books can end up with black covers on the device. I have seen this on my Glo but hadn't connected the dots. This usually happens when a few books are sideloaded in a batch and the books that end up in the "My books" tile get black covers. The import process has to open each book to get the metadata and the covers are generated by rendering the first page of an epub. That is going to hit the memory issues and as a lot of things are happening quickly, it makes it worse.
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